Matching of chiller-cooling tower to enhance efficiency of central air-conditioning plant

The influence of cooling towers on energy efficiency of central air conditioning plants was investigated based on actual operating data obtained from plants at Jurong Campus of Nanyang Technological University (NTU). Field test results show that chiller plant with undersized cooling tower delivered a higher cooling water temperature supplied to condenser and thus led to poor efficiency of the chiller plant in terms of higher kW/RT. Further studies show that for any particular system, there appear to be a critical cooling load threshold that the cold water temperature increases rapidly above this critical load. The two cooling towers under investigation recorded with critical cooling capacity of 550 RT and 650 RT respectively. During a test run at cooling load of 500 to 650 RT, system running with one cooling tower delivered the cold water at temperature of 35degreesC while operating with two cooling towers delivered cold water at 29.5degreesC. Average chiller power consumption was 525 kW with one cooling tower and 425 kW with two cooling towers when operated at a cooling load of 650 RT. The saving in power consumption of chiller outweighs the additional power for cooling tower fan.